Study on Pretightening Loss Effect of Bolt Support in Deep Soft Rock Roadway

Table 1

3-1 distribution of coal seam roof and floor slate.

Rock name	Thickness (m)	Lithologic characteristics
Gravelly sandstone or sandy mudstone	25.0	Light gray, gray white, containing rock debris and mica fragments, mudstone cementation, argillaceous filling
Sandstone mudstone and siltstone interbedding	1.6	Gray siltstone and dark gray sandy mudstone, locally containing plant fossils, with parallel bedding development
Coal seam	4.3	Black dull luster, semidark briquette, containing silk charcoal, banded structure, asphalt luster, containing p yrite
Sandstone argillaceous	1.5	Dark gray sandy mudstone, locally containing plant fossils, with developed bedding
Sandy argillaceous and siltstone interbedding	15.0	Gray siltstone and dark gray sandy mudstone, locally containing plant fossils, and developed parallel bedding